Abstract The goals of this grant are to understand the regulation of Ded1, an essential gene that promotes translation and affects mRNA storage granules. Translation is an energy intensive process and is highly regulated. Under conditions of stress, when energy levels are often low, translation is largely repressed and many mRNAs are stored in cytoplasmic RNA storage granules, such as stress granules. Ded1 is an RNA helicase that interacts with nearly all mRNAs. Ded1 can affect the formation and disassembly of stress granules and promote translation initiation, suggesting that it is poised to move mRNAs between storage and translation. As Ded1 is essential for translation and interacts with several canonical translation initiation factors, its regulation will influence whether mRNAs are translated or stored. This grant focuses on the following aims: (1) Determine how key post-translational modifications affect Ded1?s function in RNA storage and translation. (2) Identify regulators of Ded1 by isolating and identifying suppressors of growth defects from key ded1 mutants. (3) Investigate the relationship of these suppressors to mRNA storage granules, translation regulation, and Ded1?s biochemical functions. We are studying this factor in budding yeast to take advantage of powerful genetic tools, but this gene is highly conserved with its mammalian counterpart, DDX3. DDX3 is misregulated in cancers and is hijacked by viruses like HIV and Hepatitis C. By understanding how Ded1/DDX3 is regulated, we will understand the fundamental question of how Ded1 influences mRNA storage and translation and may identify how this protein is misused in disease states. This project is innovative as it focuses on multiple aspects of regulation of an RNA helicase that is critical for translation and works at the interface of translation and mRNA storage.